The question addressed is the role of Hox genes expressed in the rostro-caudal axis, in the Hox gene expression of lateral organs and whether this accounts for the position of the lateral organs. There are three specific aims. First, it is proposed to determine if the axial Hox code is used for positional information in the lateral regions of the embryo. The second aim is to fate map the individual somites that form the scapula. From earlier work the Principal Investigator proposes that the dermamyotome rather than the sleratome gives rise to the chondrocytes of the scapula. The third aim will use targeted misexpression of Hoxa-6, Hoxb-6 and Hoxc-6 into the segmental plate that will give rise to somites 7-14. Full length clones of chick Hoxa-6 and Hoxb-6 will be isolated, RCAS vectors created. Basically this approach will challenge the system to permit insight into how boundaries are established in the cervical region of the embryo.